On Mon, Jan 11, 2021 at 07:36:20PM +0100, Ard Biesheuvel wrote: > On Mon, 11 Jan 2021 at 18:27, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > On Mon, 11 Jan 2021 at 17:52, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > Special request to Peter to take a look at patch #2, and in particular, > > > whether synchronize_rcu_tasks() is sufficient to ensure that a module > > > providing the target of a static call can be unloaded safely. > > > > It seems I may have managed to confuse myself slightly here: without > > an upper bound on the size of the input of the crc_t10dif() routine, I > > suppose we can never assume that all its callers have finished. > > > > Replying to self again - apologies. > > I think this is actually correct after all: synchronize_rcu_tasks() > guarantees that all tasks have passed through a 'safe state', i.e., > voluntary schedule(), return to userland, etc, which guarantees that > no task could be executing the old static call target after > synchronize_rcu_tasks() returns. Right, I think it should work. My initial question was why you'd want to support the unreg at all. AFAICT these implementations are tiny, why bother having them as a module, or if you insist having them as a module, why allowing removal?
